The disclosed invention is directed generally to computer storage digital audio tape (DAT) drives, and more particularly is directed to a computer data storage DAT drive that automatically recognizes the presence of audio data on a DAT tape and provides for proper playback of the audio tape.
Digital audio tape (DAT) technology, which was developed for audio programming, has been adapted for storage of computer data. An example of a format for the storage of computer data utilizing DAT technology is the American National Standards Institute (ANSI) Digital Data Storage (DDS) standard, presently in draft form ("PROPOSED AMERICAN NATIONAL STANDARD HELICAL-SCAN DIGITAL COMPUTER TAPE CARTRIDGE 381 mm (0.150 in) FOR INFORMATION INTERCHANGE," ASC X3 Project No. 668-D).
The characteristics that have made DAT technology attractive for computer data storage include high capacity, high transfer rate capability, relatively small media size and low media cost, and the adaptability of DAT technology to conform with personal computer storage device form factors including the 51/4 and 31/2 inch forms.
The use of DAT technology for storage of computer data can be achieved by application of a data storage format, such as the above-referenced ANSI DDS format, to the DAT format. In particular, the DAT physical track format is retained, but the contents of the information stored in the tracks is in accordance with the computer data storage format.
As a result of the use of the DAT physical tape format, a computer storage DAT drive can provide some of the functions for reading DAT audio tapes. Thus, for example, a computer storage DAT drive would be able to extract the PCM data and the subcode information from a DAT audio tape, but typically would not recognize the tape. Nor would it have the capability of providing an audio output signal, either in digital or analog form.
A further consideration with format detection with a computer storage DAT drive is the procedure by which the tape format is detected. For example, pursuant to the DDS format, a tape is positioned near the beginning of the tape to permit unambiguous format detection, for example, for a re-recorded data tape that had been previously recorded with audio. On a DDS tape, the area containing format information is at some distance from the beginning of the tape media, and searching for the format detection area on a DAT data tape at normal playback speed takes a relatively long time. However, the format detection area on a DAT data tape is relatively small and thus cannot be read at high speeds such as .times.200 (200 times normal playback speed designated as .times.1).